Fracture treatments are utilized to improve fluid conductivity between a wellbore and a formation of interest. Hydraulic fracture treatments are typically used in low-permeability formations, or in any formation to bypass near-wellbore permeability damage. A typical treatment injects a viscous fluid to open a fracture of a desired geometry, and the viscous fluid carries a proppant into the opened fracture to maintain conductivity in the fracture after the treatment is completed. Viscous fluids have features that damage the permeability of the proppant pack and/or the formation near the fracture. For example, the fluid may have gel that is deposited in the fracture, the fluid may have surfactants that leave unbroken micelles in the fracture or change the wettability of the formation in the region of the fracture. Breakers are utilized in many treatments to mitigate fluid damage in the fracture. However, breakers and other treatments are subject to variability of results, they add expense and complication to a fracture treatment, and in all cases still leave at least some fluid damage in the fracture.
Other complications and difficulties exist in the current art of hydraulic fracture treatments. For example, the chemistry of fracturing gels, including the crosslinking of gels, creates complications when designing fracture treatments for a broad range of temperatures. After a fracture treatment, fracturing fluid that flows back to the surface must be disposed of, and the more fluid that is utilized in the treatment the greater the disposal risk and expense. Further, some fracturing fluids are not compatible with calcium brines, reducing an option for a higher density fracturing fluid and complicating fracture treatment designs in some circumstances.
Acid fracturing treatments are utilized to remove damage and/or open channels in the formation. The acid etches channels that, in theory, remain open after the hydraulic pressure is released and the formation relaxes back to a naturally pressured condition. It is desirable that the acid flow into and etch or remove damage from areas of the formation that do not flow well before the treatment. However, the highly permeable and naturally fractured areas of the formation naturally tend to accept fluid better and thereby take more of the acid than is desired. Therefore, fluid loss additives and diverting additives may be added to the acid fracturing treatment to block the high permeability channels and direct the treatment into lower permeability channels. To carry the fluid loss additives and to develop the desired fracture geometry, the acid fracturing fluid may be viscosified similar to a hydraulic fracturing treatment. The inclusion of viscosifiers and particulates in acid fracturing introduces potential damage and complications in a similar manner to hydraulic fracturing without acid.
Accordingly, there is a demand for further improvements in this area of technology.